function totop() {
	var totop = $('.u_btn_to');

	totop.on('touchstart', function () {
		$(this).addClass('u_btn_to_on');
	});
	
	totop.on('touchend', function (ev) {
		var timer = null;
		var self = this;
		var t = $(window).scrollTop();
		
		timer = setInterval(function () {
			t *= .8;

		  if (t < 1) {
				t = 0;
				clearInterval(timer);
				$(self).removeClass('u_btn_to_on');
			}
			
			document.documentElement.scrollTop = document.body.scrollTop = t;
		});
		
		ev.preventDefault();
	});
	
	$(window).on('scroll', function () {
		if ($(window).scrollTop() > $(window).height()) totop.css({'display': 'block'});
		else totop.css({'display': 'none'});
	});
}